In a vapor compression refrigerating cycle apparatus, it is known to employ an ejector as a decompressing device for decompressing refrigerant, which has been compressed into a supercritical state by a compressor and cooled through a radiator. The ejector is, for example, described in JP-A-2004-116807.
The ejector has a nozzle portion that converts pressure energy of the refrigerant flowing out from the radiator into velocity energy, thereby to isoentropically decompress and expand the refrigerant. Further, the ejector draws gas-phase refrigerant from in an evaporator by means of a high-velocity jet flow of refrigerant from the nozzle portion, and converts the velocity energy into pressure energy through a diffuser while mixing the drawn refrigerant with the refrigerant jetted from the nozzle portion, thereby to increase pressure of the refrigerant. By the increase in pressure of the refrigerant, power of the compressor can be reduced, and further a coefficient of performance (COP) of the refrigerating cycle apparatus can be improved.
In the ejector described in JP-A-2004-116807, an inner surface of the nozzle portion, which provides a refrigerant passage, is a smoothly curved surface without having corners, so as to facilitate the flow of the refrigerant by reducing occurrence of swirl flow and the like. Thus, efficiency of the ejector improves.